1. Field of the Invention
The present invention relates generally to a glass forming machine and more particularly to a valve block assembly for sequencing the operational steps of the machine.
2. Description of the Prior Art
Today, glassware is generally produced by utilizing highly complex and automated machines such as, for example, one normally referred to as an individual section glass forming, or IS machine, which is required to carry out a plurality of operational steps in its manufacture of glassware. One commonly used method of sequencing these operational steps has been to use a large rotatably mounted drum carrying a plurality of buttons or cams appropriately positioned on the surface of the drum. In this manner, as the durm is revolved about its axis, the cams sequentially contact and actuate a number of pneumatic valves which when actuated respectively initiate into operation the aforestated operational steps.
While the aforedescribed mechanical method of controlling the operational sequence of a glass forming machine carries with it certain advantages such as, for example, reliable actuation of the machines pneumatic valves, it, on the other hand, displays many disadvantages such as, for example, the cumbersome task of individually adjusting each cam in order to retime the machine. Accordingly, a second method of controlling the operational sequence of the glass forming machine, and one which is responsive to the disadvantages displayed by the mechanical method, is by electronic initiation. One example of an electronic initiating method is disclosed in U.S. Pat. No. 3,365,623 issued to David S. Stacey on Jan. 23, 1968, and entitled "Automatic Control System." In this patent, a control system which generates sequenced electrical pulses is disclosed. The pulses generated are individually fed to pulse responsive means which are part of and arranged to operate a processing apparatus such as a glass forming machine. In this manner, the aforedescribed drum actuated valves and drum can be eliminated and replaced with the pulse actuated valve means.
A more recent method of electronically controlling the operational sequence of a glass forming machine is disclosed in U.S. Pat. No. 3,762,907 to Richard M. Quinn et. al. entitled "A Glass Forming Machine Having An Automatic Control System," and assigned to the assignee of the present invention. This application also discloses the utilization of electronically actuated valve means in place of the aforedescribed drum.
While the aforedescribed electronically controlled systems display many advantages over the prior art such as, for example, the accurate manner in which they control the sequence of a glass forming machine or the ease in which they allow retiming of the sequence, they do provide room for improvement. For example, electrically or pulse actuated valve means have been found on occasion to stick due to the rather hostile environment in which a typical glass forming machine is used. If this happens, it is readily apparent that the overall sequential operation of the machine would be interrupted which, in turn, could cause delay in the production of glassware. In addition these types of electronically controlled systems often utilize a common air supply for pneumatic operation and common lubrication supplies which only add to the sticking valve problem.